Note: Descriptions are shown in the official language in which they were submitted.
CA 02709062 2010-07-06
HEAT PUMP WATER HEATER AND ASSOCIATED CONTROL SYSTEM
BACKGROUND OF THE INVENTION
100011 This invention generally relates to liquid heating apparatus and, in
a representatively
illustrated embodiment thereof, more particularly relates to a specially
designed heat pump water
heater and associated control system.
[00021 In the past, various proposals have been made for operatively
coupling a heat pump to
an electric water heater to controllably add refrigerant heat to the water
stored in the tank portion
of the water heater during water heating demand cycles. Since the coefficient
of performance of
a heat pump is considerably better than the coefficient of performance of the
electric resistance
type heating structure of an electric water heater, this use of a heat pump
provides an opportunity
to substantially reduce the operating cost of an electric water heater to
which it is operatively
coupled, with the electric heating structure being available as a supplemental
water heating
mechanism should the heat pump fail or need heating supplementation.
100031 As is well known in the water heater art, there is a tradeoff between
the heating cost
effectiveness of a heat pump and the more rapid water heating capability of an
electric heating
element. In conventionally constructed heat pump water heaters the user
typically has little if
any ability to selectively adjust the relationship between water heating cost
effectiveness and
water heating rapidity in the water heater to suit varying operating
environments and hot water
demand situations. An additional need that exists in the heat pump water
heater area is the need
for improvements in the placement and component arrangement of the heat pump
portion of the
water heater. It is to these needs that the present invention is primarily
directed.
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SUMMARY OF THE INVENTION
100041 In carrying out principles of the present invention, in accordance
With
representatively illustrated embodiment thereof. liquid heating apparatus is
provided that
comprises tirst apparaus operative to transfer refrigerant heat to a liquid.
second apparatus
operative to transfer electrical heat to the liquid. and a control system. The
liquid heating
apparent, illustratively includes an electric water heater having a tank for
storing water to be
heated, the tirst apparatus illustratively includes a refrieerant circuit
structure, preferably :a
heat pump. operatively coupled to the electric water heater, and the second
apparatus
illustratively includes an electric- resistance type heating structure
extending through an
interior portion of the tank.
[0005] According to an aspect of the overall invention. the control--system
may have a
heating mode operative. in a heating cycle initiated in response to a sensed
demand for liquid
heating, to initially utilize the first apparatus. at the start of the heating
cycle, to transfer
refrigerant heat to the liquid while preventing operation of the second
apparatus for a
predetermined lockout time period, thereafter utilize the second apparatus to
supplement the
refrigerant heating of the liquid with electrical heating thereof if the
heating demand has not
been satisfied by the previous refrigerant heating of the liquid, and then
terminate the
operation of both the first heating apparatus and the seeond heating.apperatus
at the end of
the heating cycle when the demand for liquid heating is satisfied. The lockout
of the second
apparatus during each heating cycle in this heating mode is illustratively
initiated.only at the
start of .such heating cycle.
100061 according to other aspects of the overall invention. the. First
apparatus may
include a water circuit coupled to the tank and having a pump operative to
draw water from a
bottom portion of the tank and return the water to a top portion of the tank,
the first apparatus
may include a compressor, and the control system may he operative, if
necessary, to utilize
the second apparatus to heat the liquid to a predetermined minimum temperature
prior to
permitting operation of the compressor.
(00071 According to a further aspect of the overall inventiian, the control
system may
he operative to control the first apparatus and the second apparatus in either
one of user-
selectable first and second heating modes. The tirst heating mode. when
selected, is
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operative in response a sensed demand for liquid heating to initially utilize
the first apparatus
to transfer refrigerant heat to-the liquid. while preventing operation of the
second apparatus
for a predetermined first lockout time period, and thereafter utilize the
second apparatus to
supplement the refrigerant heating of the liquid with electrical heating
thereof if the heating
demand has not been satisfied by the previous refrigerant heating of the
00081 The second heating mode, when selected, is operative in response a
sensed
deatand for liquid heating to initially- utilize the first apparatus to
transfer refrigerant heat to
the liquid. while preventing operation of the second apparatus for a
predetermined second
lockout time period of a different magnitude than the first lockout time
period.and thereafter
utilizing the second apparatus to supplement the refrigerant heating of the
liquid with
electrical heating thereof if the heating demand has not been satisfied by the
.previous
refrigerant heating of the liquid.
[0009i The control system rua)- be additionally operative to control the first
apparatus and the
second apparatus in a third user-selectable heating mode which. when selected;
is operative
fOr only. a predetermined time period to utilize only the second apparatus to
'transfer electric
heat to the liquid in response to a sensed demand for liquid heating, the
control system, after
the expiration of the predetermined time period, automatically selecting one
of the first and
second heating modes tbr use in satisfying a sensed liquid heating demand.
1.0010.1 According to a further aspect of the overall invention, the
control system May
be operative to control the first apparatus and the second apparatus in either
one. of user-
selectable first and second heating modes. The first heating mode, when
selected, is
operative to utilize the first apparatus and, if needed. the second apparatus
to transfer heat to
the liquid in response to a sensed demand for liquid heating. The second
heatinganode. when
selected. is operative. for only a predetermined time period, tO utilize only
the second
apparatus to transfer heat to the liquid in response to a sensed demand for
liquid beafiag, the
control system. alter the expiration of the predetermined time period,
automatically selecting
the first heating mode for use in satisfying a sensed liquid heating demand.
[001 11 According to another aspect of the overall invention, the control
system is
operative to receive a desired liquid heating temperature set Point input by a
user of the
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liquid heating apparatus, and having a user-selectable first heating mode
which, in response
to a sensed demand for liquid heating. initially utilizes the first apparatus
to transfer
refrigerant heal to the liquid, while preventing operation of the second
apparatus for a
predetermined first lockout time period, and then utilizes the second
apparatus to supplement
the refril...!erani heating of the liquid with electrical heating thereof if
the heating demand has
not been satisfied by the previous refrigerant heating of the liquid. if the
user-input
temperature set point is equal to or greater than a predetermined magnitude,
the control
s),. stein is automatically operative to implement a second heating mode
similar to said first
heating intxlc but having a predetermined second lockout time period greater
than the first
lockout time period.
BRIEF DESCRIPTION OF THE DRAWINGS
[00121 An embodiment of the invention will now be described by way of an
example
only with retimmee to the accompanying drawings in which:
100131 (Ai. 1 is a schematic diagram of the water heater .and control
system;
10014] flti. 2 is a partially cut away perspective view of the WOW heater;
and
100151 FIGS. 3A and 313 combinatively tbrm a schematic flow diagram
illustrating
various control techniques utilized in conjunction with the water heater and
associated
control 53. tc.in.
.....
,
,
õ..:
_ =
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DETAILED DESCRIPTION
INA Turning first to PIGS. 1 and 2, liquid heating apparatus
representatively embodying
principles of the present invention is designated generally by the reference
numeral 10 and
illustratively includes an electric water heater 12, a refrigerant circuit
illustratively in the form of
a heat pump 14, and a specially designed control system 16.
100171 Water heater 12 has a vertically elongated cylindrical storage tank
18 for holding a
quantity (representatively fitly gallons) of water to be heated. The tank 18
has a side-mounted
cold water inlet 20 adjacent its lower end for receiving pressurized cold
water from a source
thereof, and a side-mounted hot water outlet 22 adjacent its upper end through
which heated
water may be periodically delivered, on demand, to hot water-utilizing
fixtures such as sinks,
bathtubs, showers, dishwashers and the like. Upper and lower electrical
resistance heating
elements 24,26 respectively extend through upper and lower interior portions
of the. tatik 18. An
upper tank thermistor 28 senses an upper tank water temperature, and a lower
tank thermistor 30
senses a lower tank water temperature.
[0018) With continuing reference to FIGS. 1 and 2, the heat puny 14 (which
may
alternatively be another type of refrigerant circuit structure) includes a
refrigerant piping circuit
32 in which a compressor 34, a condenser coil 36, an expansion valve 38 and-an
evaporator coil
40 having an associated evaporator fan 42 are connected in series as
Schematically depicted in
FIG. 1. During operation of the heat pump 14, the compressor 34 forces
refrigerant from its
outlet through the piping circuit 32 sequentially through a first flow passage
.44in the condenser
coil 36, the expansion valve 38, the evaporator coil 40 and back into the
inlet of the compressor
34.
[0019) A second flow passage 46 (see FIG. 1) extends through the condenser
coil 36 and is in
thermal communication with the first condenser coil flow passage 44. A water
pump 48 has its
inlet coupled to a lower interior end portion of the tank 18 by.a pipe .50,
and its outlet coupled to
the inlet of the condenser coil flow passage 46. The outlet of the flow
passage 46 is coupled to
an upper interior end portion of the tank 18 by a pipe 52. Accordingly, during
operation of the
heat pump compressor 34 and the water pump 48, heat from compressed
refrigerant traversing
the condenser coil passage 44 is transferred to water being pumped from the
tank 18 through the
CA 02709062 2013-05-21
condenser coil passage 46 and back to the tank 18 via the pipes $0 and 52 to
thereby transfer
refrigerant heat to the tank water.
[0020] A thermistor 54 senses the ambient temperature; a thermistor 56.
senses the
compressor discharge temperature; a thermistor 58 senses the. evaporator coil
inlet temperature; a
therinistor 60 senses the evaporator coil suction temperature; and a
thermistor 62 senses the
condenser coil water discharge temperature. While the above-mentioned
temperature = sensing
devices arc representatively thermistors, it will be readily apparent to those
of skill in this
particular art that various other types of temperature sensors could
alternatively be utilized
without departing from principles of the present invention.
pail As shown in FIG. 2, the heat pump 14 is representatively mOunted on
the upper end of
the water heater tank IS. with the evaporator coil 40 having a partially
annular configuration
which, in conjunction with associated top and side wall structures (removed in
FIG. 2 for
purposes of illustrative clarity) bounds a plenum 63 disposed on the upper end
of the tank 18.
The compressor 34 and the condenser coil 36 are disposed within the plenum 63.
The evaporator
fan structure 42 is centrally disposed on the top side of the annularly curved
evaporator coil 40
and is operative to flow ambient air downwardly into the plenum 63 and then
horizontally
outwardly through the evaporator coil 40. This unique arrangement of the
components of the
heat pump 14 advantageously increases its operating efficiency by transferring
both fan heat and
compressor heat to the evaporator coil 40 via air being forced through the
plenum 63 by the fan
42. Of course, the heat pump 14 could be mounted on the water heater 12 in a
different manner,
or be positioned remotely therefrom, if desired.
[00221 Referring again to FIG. I, the control system 16 ineludes..a
microprocessor 64
preprogrammed to provide the water heater 12 and the heat pump 14 with a
variety of
subsequently described operational modes and control sequences that .provide
the water heating
apparatus 10 with desirably enhanced operational flexibility and efficiency.
Control system 16
also includes a user input touchpad input panel 66 that may be .conveniently
mounted on the
exterior of the water heater tank 18 at a suitable location thereon.
[0023] In the representatively illustrated form thereof, the touchpad 66
has disposed on the
face thereof up and down temperature setting arrows 68,70 which may be pressed
by a user to
increase or decrease the selected desired tank water temperature setting. To
the right of the
arrows 68,70 is a vertical column of temperature setting indicating lights
72,74,76,7S,80,82 that
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respectively correvonti to six user-selected water temperature settings having
magnitudes that
increase vertically from indicating light 72 to indicating light 82. Thus, for
example, if the user
wants to select a "normal" water temperature to be maintained in the tank 18
the user simply
presses one of the temperature setting arrows 68,70 one or more times until
the. indicating light
76 is illuminated, indicating that a "normal" tank water temperature setting
has been selected.
[0024] At the lower end of the touchpad 66 are four .mode selection areas
84,86,88 and 90
which may be pressed by a user to select manners in which the water heating
apparatus 10 will
function. These touchpad areas 84,86,88,90 respectively correspond to an
"energy saver" mode,
a "normal" mode, an "oft" mode, and an "electric heat only" mode. Pressing the
"energy saver"
area 84 illuminates a corresponding indicating light 84a on the touchpad 66,
preSsing the
"normal" area 86 illuminates a corresponding indicating lied 86a on the
touchpad 66, and
pressing the "electric heat only" area 90 illuminates a corresponding
indicating light 90a on the
touchpad 66.
pe251 As will be subsequently described in greater detail herein, the
energy saver mode of
the control system 16 assists the water heater 12 in obtaining maximum
efficiency, The normal
mode, on the other hand, is geared to maximizing the performance of the water
heater 12 while
still providing good energy savings. Each. of these two modes, in a
predetermined, -somewhat
-different manner, first utilizes heat pump energy. (in the form of
refrigerant heat) to raise the
water heater tank temperature before additionally utilizing electric heat if
needed to fulfill a
water heating demand. When selected, the electric heat only mode utilizes only
electric heat to
meet water heating demands, but is automatically limited to a set operational
time period built
into the control system. Upon expiration of this time period, the control
system automatically
returns the water heater to its previously selected normal or energy saver
Mode.
[00261 Turning now to the flow chart of FIGS. 3A and 3B, the modes and
operational
sequences of the water heater 12, carried out by the control system 16, will
be more fully
described. With initial reference to FIG. 3A, the water heating apparatus 10
is initially powered
up at the start step 92 (by user selection of the energy saver, normal or
electric heat only mode)
after which a transfer is made to pre-warm test step 94. At step 94 a query is
made as to whether
the lower tank temperature (as sensed by thermistor 30) is less than a
predetermined temperature
(representatively 70 F) and the upper tank temperature (as sensed by the
therrnistor 28) is less
than or equal to a predetermined temperature (representatively 75 P).
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100271 If both of these sensed temperature conditions are met, the control
system 16 effects a
transfer to step 96 at which a pre-warrn cycle is initiated to heat the tank
water to a
predetermined minimum temperature (representatively 80t) to protect the
compressor.34, at its
subsequent start-up, by assuring that its initial discharge temperature (as
Measured by thermistor
56) is sufficiently high to prevent damage to the compressor 34. In response
to the pre-warm
cycle being initiated at step 96. the control system 16 energizes the water
pump 48 at high speed,
and energizes both of the electric heating elements 24 and 26. A transfer is
then made to step 98
at which a query is made as to whether the sensed lower tank temperature is
equal to or greater
than its predetermined minimum temperature. While the answer to this query is
negative, the
tank water temperature continues to be monitored at step 98 until the query
answer becomes
positive, at which point the electric heat is de-energized at step 100 and a
subsequent transfer is
made to step 102.
[00281 At step 102 a query is made as to whether the tank water needs heat.
If it does not, the
control system 16 maintains the operational sequence at step 102 until it is
determined at such
step that the tank water does need beat from the water. heating apparatus 10,
at which point a
transfer is made to step 104. At step 104 a query is made as to which
operational mode (i.e., the
energy saver mode, the normal mode or the electric heat only mode) has been
selected. If the
energy saver mode has been selected a transfer is made to step 106. At step
106, the heat pump
14 is started, to deliver refrigerant heat.(via the circulation of water
through pump 48) to the tank
water, and electric heat is locked out for a predetermined delay period
(representatively 45
minutes).
10291 .A transfer is then made to step 108 where a query is made as to
whether the tank water
needs heat. If the tank water does not need heat, atransfer is made back to
step 102 Wherein the
system waits until there is another call for tank water heating. If it is
determined at step 108 that
the tank water does need heat, a transfer is made to step 110 at which a query
is made as to
whether the previously set electric heat delay (or "lockout") period set at
step 106 has expired. If
such delay period has not expired, the system continues to loop through steps
108,109 as
indicated, until the delay period expires, at which point a transfer is made
to step 112 (see PIG.
38) at which point the electric heating of the tank water is initiated by
energizing the upper
electric heating element 24. Next, at step 114 a query is made as to whether
the tank water needs
heat. If it does, the system stays at step 114 until the step 114 query answer
becomes negative, at
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which point both refrigerant and electric heating of the tank water are
terminated, and 4 transfer
is made back to flow chart point 116 (see FIG. 3A).
100301 An adaptive mode, associated with the energy saver mode, is also
preferably pre-
programmed into the control system 16. If, at step 106, the user-selected tank
water set point
temperature is at or above a predetermined threshold magnitude
(representatively, 130 F), the
adaptive mode is automatically initiated by the control system 16 in place of
the energy saver
mode to further increase the efficiency of the water heating apparatus 10.
When this adaptive
mode is automatically initiated at step 106, the electric heat delay period is
set to a lesser time
period (representatively 20 minutes) than in the energy saver mode, and a
transfer is made to step
108 as previously described.
100311 If at step 104 in FIG. 3A it is determined that the normal mode has
been selected by
the user, a transfer is made to step 118 at which point the heat pump 14 is
started, to -deliver
refrigerant heat to the tank water, and electric heat is locked out .for a
predetermined, delay period
(representatively 30 minutes).
[00321 A transfer is then made to step 120 where a query is made as to
whether the tank water
needs heat. If the tank water does not need heat, a transfer is made back to
step 192 wherein the
system waits until there is another call for tank water heating. If it is
'determined at step 120 that
the tank water does need heat, a transfer is made to step 122 at which a query
is made as te
whether the electric heat delay (or "lockout") period set at step 118 has
expired. If such delay
period has not expired, the system continues to loop through steps 120,122 as
indicated, until the
delay period expires, at which point a transfer is made to step 124 (see FIG.
3B) at which the
electric heating of the tank water is initiated by energizing the upper
electric heating element 24.
Next, at step 126 a query is made as to whether the tank water needs heat. If
it does, the system
stays at step 126 until the step 126 query answer becomes negative, at which
point both
refrigerant and electric heating of the tank water are terminated, and a
transfer is made back to
flow chart point 116 (see FIG. 3A).
i00331 A normal high temperature mode, associated with the normal mode, is
also preferably
pre-programmed into the control system 16. If. at step 118, the user-selected
tank water set point
temperature is at or above a- predetermined threshold magnitude
(representatively, 130 F), the
normal high temperature mode is automatically initiated by the control system
16 in place of the
normal mode to further increase the efficiency of the water heating apparatus
10. When this
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normal high temperature mode is automatically initiated at step 118, the
electric heat -delay
period is set to a lesser time (representatively 15 minutes) than in the
normal mode, and a
transfer is made to step 120 as previously described.
tO0341 If at step 104 in FIG. 3A it is determined that the electric heat
only mode has been
selected by the user, a transfer is made to step 128 at which point only the
electric heat is
energized (illustratively by energizing both of the upper and tower electric
heating elements 24
and 26), without the heat pump 14 being utilized in this water heating mode.
Preferably, also at
step 128, a timer is automatically set (representatively for a two week time
period). At the next
step 130 a query is made as to whether tank water heating is needed. flit is,
the system remains
at step 130 until the tank water heating demand is satisfied at which point a
transfer is made back
to step 102 to await another electric heat-only heating demand. After
expiration of the
previously set timer period, the system automatically reverts to the
previously set energy saver or
normal mode (or to the default energy saver mode if one of these two modes was
not selected
before the electric heat only mode was selected). Additionally, at any time
during this
automatically set timer period the user may manually reset the system-to
another heating mode if
desired.
[00351 The foregoing detailed description is to be clearly understood as
being given by way
of illustration and example only, the spirit andscope.of the present invention
being limited solely
by the appended claims.
